Dennis,
I just saw your email.
Commercial radiotelegraphers adjusted their semi-automatic keys to produce 8 to 10 dots, and when they sent on their straight keys they made the dots heavy to counteract tropical static. I have heard from UK operators who were seeking employment that they sent their dots too lightly and weren't hired!
The close spacing that some Amateurs use for their semi-automatic keys wasn't used at sea because on the average day there was enough mechanical vibrations from the ship's engines, that the spacing had to be wider. When rougher weather was encountered, we learned to widen the vibrator gap even more and lastly when we were in a violent storm we had to abandon the Vibroplex and use a straight key - or if you had some foresight, a sideswiper which was faster than the straight key for many operators.
73
DR
N1EA